A process has been developed to remove a depression in a floor, particularly a concrete floor, by which comprises injecting under the floor polyurethane foam until the floor reaches the desired level. Such a process is described for instance in Canadian patent 1,210,605 dated 86.09.02 as invented by HAKKINEN.
It has been found however, that if one follows the teaching of merely injecting polyurethane, problems arise and the floor has a tendency to sink again in certain circumstances, particularly when heavy loads are exerted on concrete floors.